As cellular communication technologies continue to evolve, a heavy emphasis has been placed on conserving network resources, enhancing reliability, and increasing data rates. One way to conserve network resources, while simultaneously enhancing reliability and increasing data rates, is through the use of device-to-device (D2D) communication. D2D communication allows wireless communication devices in close proximity to one another to communicate directly, rather than by routing traffic between the devices through one or more cellular access points (e.g., evolved Node Bs (eNBs)). Using D2D communication reduces traffic to one or more cellular access points in a wireless communication network, and can improve the performance of data transfer between wireless communication devices.
D2D communication enables a number of potential gains over traditional cellular routing techniques. First, radio resources between the resource layer on which D2D communication occurs and the resource layer on which cellular communication occurs can be shared. That is, a wireless communication device may simultaneously utilize a D2D connection and a cellular connection, thereby enhancing data rates of the wireless communication device. Additionally, wireless communication devices using D2D will experience a hop gain, due to the fact that one or more cellular access points are not required for routing data between the devices. Further gains may be achieved due to favorable propagation conditions between wireless communication devices due to the proximity of the devices, which may allow for high peak data rates. Finally, end-to-end latency may decrease between wireless communication devices using D2D communication, due to the short-cutting of cellular access point routing and thus the forwarding time of data between the devices.
In most D2D communication systems, D2D discovery is the first step in the establishment of a D2D communication link. Generally, D2D discovery is made possible by the transmission and receipt of discovery messages, or beacons, between wireless communication devices. In conventional D2D communication systems, a broadcasting wireless communication device will transmit a discovery message, which may be received by a discovering wireless communication device. Generally, the broadcasting wireless communication device is considered “discovered” (i.e., the D2D discovery status of the broadcasting wireless communication device is determined as positive) according to conventional D2D communication systems once a single discovery message is detected at a lower layer of the protocol stack of the discovering wireless communication device (i.e., Layer 1). The discovering wireless communication device may then choose to initiate a D2D wireless communication link with the broadcasting wireless communication device.
While generally effective for stationary wireless communication devices, the foregoing device discovery process produces significant errors when used with mobile wireless communication devices. First, when used by mobile wireless communication devices, the D2D device discovery process described above results in a high probability of false detections due to the fact that the broadcasting wireless communication device may have moved out of range of the detecting wireless communication device shortly after receipt of the discovery message. Accordingly, if the detecting wireless communication device should attempt to initiate a D2D wireless communication link with the broadcasting wireless communication device, the D2D wireless communication link would fail. Second, discovery messages broadcast from a mobile wireless communication device may fail to be detected altogether due to the large variance in discovery message characteristics caused by changes to the location and/or orientation of the broadcasting wireless communication device.
Accordingly, there is a need for a reliable D2D discovery method capable of improving detection of D2D wireless communication devices in a cellular communications network.